Plural function circuit



y 3, 1949. R. H. STAFFORD 2,469,281

PLURAL FUNCTION C TRCUIT Filed July 8, 1946 IN V EN TOR.

B'Mafdflffa/jbrd BY QQM Patented May 3, 1949 PLURAL FUNCTION CIRCUIT Richard H. Stafford, Lamoni, Iowa, assignor to Radio Corporation of America, a corporation of Delaware Application July 8, 1946, Serial No. 681,902

6 Claims. 1

This invention relates to plural function circuits and more particularly to an electron discharge device circuit which is readily controlled to operate either for the purpose of amplifying a radio signal or for the purpose of triggering an external circuit controlling a switching operation or the like.

In connection with signal channels of various types, it is frequently desirable to provide means for producing a switching effect. The accomplishment of this purpose has usually involved. the provision of extra vacuum tubes and extra circuit elements. In accordance with the present invention, means are provided for switching the connections of an electron discharge device so that it may function either asv one stage of a signal amplifying channel or as means of changing the connections of another circuit.

The invention is applicable to various types of signal channels. It is illustrated as applied to an intermediate frequency channel including a grounded grid amplifier and having the signal to be amplified injected into its cathode lead. The control grid circuit of this amplifier includesa capacitor which is short-circuited during its. operation as an amplifier. When it is to be operated as a switching control tube, however, (1) the short circuit is removed from the grid capacitor, (2) its cathode is connected to ground,

(3) a resistor is connected in shunt to its output circuit for starting current through it, and (4) a switch potential is applied to its control grid. These various switching operations may be effected successively by the control knob of a double pie switch or the equivalent.

The principal object of the invention is to provide an improved arrangement and method of operation whereby a stage of a. signal amplifying channel may be utilized for purposes other than amplification. Additional objects are to provide simple circuit elements and switching means for connecting an electron discharge device to operate alternatively as a grounded grid amplifier or as a circuit switching element.

The invention will be better understood from the following description considered in connection with the accompanying drawing and its scope is indicated by the appended claims.

The single figure of the drawing is a wiring diagram of a preferred embodiment of the invention.

This figure shows an intermediate frequency channel including an amplifier iii, a transformer ll, an amplifier l2 and a transformer l3. Operating potential is applied from a +3 terminal (1) through the tuned primary circuit l t-t5 of the transformer I l to the anode [6 of thev amplifier l0, (2) through a relay operating coil l1 and the tuned primary circuit l 8--l 9 tothe anode of the amplifier i2, and ('3) through a resistor 2| to the shield grid 22 of the amplifier t2. Radio frequency bypass capacitors 23, 24 and 25 are shunted respectively across the shield grid circuit of the amplifier l2, the relay coil H and a resistor 26 connected in the cathode lead of the amplifier I2. The tuned secondary circuit 2'128 of the transformer H is connected in this cathode lead in series with the resistor 26.

During operation of the device II as an amplifier, a double pie switch 29 is in its right hand closed position, a signal is applied from the transformer H to the cathode 32 of the device i2 and the amplified signal is delivered at the tuned secondary' circuit 30-3! of the transformer l-3 The double pie switch 29 includes a pair of blades 33 and 34 which are rotated by a single control knob as indicated by a broken line 35. When this switch is closed to the right, its blade 34 short circuits a capacitor 36- whichconnected between ground and a grid 31 of the device l2,

and this device is connected to function as a grounded grid amplifier.

When the switch blades 33 and 34 are rotated in a counterclockwise direction (1) the blade 36 connects the cathode 32 to ground through a lead 31 and (2) connects a, resistor 38 in shunt to the output circuit of the device 12 for starting current through it. At the same time, the blade 33 connects the grid 3? through a lead 39- and a resistor 40 to a terminal ll from which there is applied a positive potential of such value as to maintain the output current of the device 12 and to produce operation of a relay 42. Further rotation of the blades 33 and 34 successively disconnects the grid 3! from the positive terminal, opens the ground connection of the cathode 32, connects the grid 31 through a resistor 43 to a negative terminal 44 so that the coil I1 is sufficiently deenergized to operate the relay 42 and finally short circuits the grid capacitor 33.

The invention thus provides a simple and easily controlled means for adapting one stage of a signal channel to operate alternatively as an amplifier or as a device for producing a control potential which may be used for switching operations or the like.

I claim as my invention:

1. The combination of an alternating current amplifier including a first stage having an output circuit, a second stage including an electron discharge device having a grid for controlling current conduction between its cathode and anode and having its cathode connected to ground through means coupled to said output circuit, a circuit tuned to said alternating current, a device responsive only to unidirectional current, means for applying operating potential to said anode through said tuned circuit and said device, a capacitor connected between said grid and ground, an impedance device, and a switch arranged to be closed in one position for short circuiting said capacitor and to be closed in another position for grounding said cathode and connecting said impedance means between said cathode and anode.

2. The combination of an alternating current amplifier including a first stage having an output circuit, a second stage including an electron discharge device having a grid for controlling current conduction between its cathode and anode and having its cathode connected to ground through means coupled to said output circuit, a circuit tuned to said alternating current, a device responsive only to unidirectional current, means for applying operating potential to said anode through said tuned circuit and said device, a capacitor connected between said grid and ground, an impedance device, means for applying unidirectional potential of positive polarity, and a switch arranged to be closed in one position for short circuiting said capacitor and in another position for grounding said cathode, connecting said impedance means between said cathode and anode and connecting said unidirectional potential applying means to said grid.

3. The combination of an alternating current amplifier including a first stage having an output circuit, a second stage including an electron discharge device having a grid for controlling current conduction between its cathode and anode and having its cathode connected to ground through means coupled to said output circuit, a circuit tuned to said alternating current, a device responsive only to unidirectional current, means for applying operating potential to said anode through said tuned circuit and said device, a capacitor connected between said grid and ground, an impedance device, a circuit having positive and negative terminals, and a switch arranged to be closed in a first position for short circuiting said capacitor, to be closed in a second position for grounding said cathode, connecting said impedance device between said cathode and anode and connecting said positive terminal to said grid and to be closed in a third position for connecting said negative terminal to said grid.

4. The combination of signal input means, an electron discharge device having a grid for controlling current conduction between its cathode and anode and having its cathode connected to ground through said signal input means, a circuit tuned to said signal, a device responsive only to unidirectional current, means for applying operating potential to said anode through said tuned circuit and said device, a capacitor connected between said grid and ground, an impedance device, and a switch arranged to be closed in one position for short circuiting said capacitor and to be closed in another position for grounding said cathode and connecting said impedance device between said cathode and anode.

5. The combination of signal input means, an electron discharge device having a grid for controlling current conduction between its cathode and anode and having its cathode connected to ground through said signal input means, a circuit tuned to said signal, a device responsive only to unidirectional current, means for applying operating potential to said anode through said tuned circuit and said device, a capacitor connected between said grid and ground, an impedance device, a direct current circuit, and a switch arranged to be closed in a first position for short circuiting said capacitor and to be closed in a second position for grounding said cathode, connecting said impedance device between said cathode and anode and connecting the positive terminal of said direct current circuit to said grid.

6. The combination of signal input means, an electron discharge device having a grid for controlling current conduction between its cathode and anode and having its cathode connected to ground through said signal input means, a circuit tuned to said signal, a device responsive only to unidirectional current, means for applying operating potential to said anode through said tuned circuit and said device, a capacitor connected between said grid and ground, an impedance device, a direct current circuit, and a switch arranged to be closed in a first position for short circuiting said capacitor, to be closed in a second position for grounding said cathode, connecting said impedance device between said cathode and anode and connecting the positive terminal of said direct current circuit to said grid, and to be closed in a third position for connecting said grid to the negative terminal of said direct current circuit.

RICHARD H. STAFFORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,980,816 McDill Nov. 13, 1934 2,357,371 Wolfner 2D Sept. 5, 1944 2,403,609 Perkins July 9, 1946 

